I think this too, R&D timeline isn't the same as product release timeline. I remember when the iPad came out, everyone was all, "this is just a bigger iPhone". But I mean, after prototypes and so on slowly leak out, it is a sure bet that Apple started making a tablet before they would a phone, so the opposite is far more likely, that the iPhone we got was a small iPad!It is odd I always pictured aplle works on phone designs one after another. The designed the iPhone, then 3g, 4, 5 etc. It seems that apple actually designed all of them at the same time. Some prototypes have looked like unevolved versions of iphone, 4, and expected 5. So it seems they are probably working on all these designs at once and release the most finished feeling one every two years. These designs were all started a bunch of years ago. We also haven't seen prototypes for anything that looks past the 5 design wise. This could mean that the more recent unreleased prototypes will be the iPhone 6, 7, etc.